The present invention concerns processes for the production of 4-[ethyl-(2'-hydroxyethyl)-amino]-1-[(2'-hydroxyethyl)-amino]-2-nitro-benz ene (I), ##STR1##
The compound of formula (I) is a blue dye, which can be employed in hair coloring compositions based upon its outstanding coloring characteristics as well as its very good physiological compatibility.
Several techniques are already known for the production of substituted nitro-p-phenylene diamine compounds of the type of formula (I). However, they are unsatisfactory from many points of view. It has thus been suggested, for example, to produce certain nitro-p-phenylene diamines by means of nitration of the corresponding p-phenylene diamine derivative. With these processes, however, the hydrogen atoms of the amino group must be protected before the nitration, by means of acetylation, formylation, tosylation, oxalylation of the production of urethane. After the following nitration, an additional hydrolysis stage is necessary for splitting off these protective groups. The result is that these processes are complicated and time-consuming, and lead to the desired nitro-p-phenylene diamine derivatives only in low total yields. These processes are also unsuitable also from the economical viewpoint. It is moreover known, from GB-PS 867 220 and the work of J. F. Corbett and A. G. Fooks, J. Chem. Soc. (C), pages 1136 to 1138, 1967, that N-1-mono-substituted 2-nitro-p-phenylene diamine cannot be produced by direct nitration of p-phenylene diamines.
According to another known process, 2,4-dinitro-aniline is catalytically reduced to 2-nitro-p-phenylene diamine (see, for example, GB-PS 955 743). In connection therewith, the isomer 4-nitro-o-phenylene diamine can form during the reduction, separation of which is difficult and time-consuming.
A process is described in DE-PS 1 768 999 which avoids an alkylation in position N-1. However, this process does not make possible the production of compounds which possess two different alkyl or hydroxyalkyl groups in the N-4 position. Moreover, the exchange reaction described in this reference proceeds with satisfactory yields only in the case of the 1-fluoro-compound, but not for the case of the corresponding chloro-compound.